In the Forgotten Realms, every third completion of a quest chain will provide a reward list with a 50% chance for each item that could have normally appeared in that list to appear. Completions which are not the third or a subsequent multiple of three have a 25% chance for those items to appear. Only the ML23 versions of the items are available in this way.

The end reward of the whole chain given by NPC Rina Belostos after completing all of above quests (called Netherese Legacy in your quest journal) is a mix of items that can be pulled from one of the optional chests in the chain (e.g. Nether Grasps), as well as 3 Commendations of your choice. So a player has the chance to pull an item directly in one of the quests or get it at the end of the chain.

Note that you can talk to Rina and run the chain again - in any order, as long as you do all five quests - for another reward.
NOTE: Named items that can appear on this end reward list will have a 100% chance of appearing on every third completion of the story arc.
You can select from one of these items when talking to Rina Belostos in the Eveningstar at the end of the quest chain. All items are Bound to Character on Equip, and are the Epic Normal (ML 23) version.